Conventional elemental mercury sources for MOCVD typically include an open container, such as a dish, of mercury disposed upstream from a susceptor, the susceptor having a substrate disposed thereon. One zone of a furnace is employed to heat and vaporize the mercury while a separate, independent, zone is used to heat the susceptor. In order to prevent the condensation of the vaporized mercury as it passes from the first to the second zone the walls of the MOCVD reactor are typically heated.
As can be appreciated, the disadvantages of such conventional MOCVD systems are several. Firstly, it has been found that the maintenance of a Hg-saturated atmosphere over the substrate requires a large mercury consumption rate. Secondly, as previously mentioned, the walls of the MOCVD reactor must be heated because the mercury container is remote from the substrate and is disposed within a separate, independent zone of the furnace. Thirdly, inasmuch as the reactor must consequently contain such a two zone furnace the design of the reactor is complicated and the flexibility of the reactor to readily accommodate configuration changes is compromised. And fourthly, inasmuch as the container of mercury is located within the MOCVD reactor during a growth run, the mercury within the container is not readily replenished. This results in a "skin" or coating of mercury compounds forming upon the surface of the liquid mercury within the container. This coating often interferes with the vapor transport of the mercury from the container to the atmosphere of the reactor.